A device, which supplies a patient with medical fluid such as an analgesic medicine at a uniform amount per hour, has been used in the art. Such a medical fluid supply device has a medical fluid chamber which stores the medical fluid, and a medical fluid tube which allows the medical fluid discharged from the medical fluid chamber to flow to an injection needle or a catheter inserted into the body of a patient.
Further, a medical fluid supply device equipped with a medical fluid injector, which is held in the hand of a patient and can be operated by the patient for patient-controlled analgesia, has been used in the art. Such a medical fluid injector is connected to the medical fluid tube of the medical fluid supply device and temporarily stores a predetermined amount of the medical fluid. As the patient manipulates the medical fluid injector by himself, the medical fluid stored in the medical fluid injector is supplied to the patient together with the medical fluid supplied by the medical fluid supply device, and thus can temporarily increase the amount of the medical fluid supplied to the patient. For example, International Application Publication No. WO 03/066138 A1 discloses an example of a medical fluid supply device which supplies medical fluid by means of pressure of a gas, and an example of a medical fluid injector.
An example of a medical fluid injector of prior art is shown in FIG. 1. Referring to FIG. 1, the medical fluid injector 10 of the prior art has a housing body 11 and a push button 12, which is exposed on a flat upper surface of the housing body 11 and can be pushed by a patient. Further, the medical fluid injector 10 has a reservoir bag (not shown), which temporarily stores medical fluid, below the push button 10 within the housing body 11. The medical fluid from a medical fluid chamber of a medical fluid supply device is stored in the reservoir bag through a tube 13A. If the reservoir bag discharges the medical fluid, which is stored in the reservoir bag, in response to pressing applied by the push button 12, the discharged medical fluid is injected to the patient through a tube 13B.
As illustrated in FIG. 1, the housing body 11 of the medical fluid injector 10 of the prior art has a flattened shape, and the push button 12 is exposed on the flat upper surface of the housing body 11. Thus, it is easy for the push button 12 to be pressed carelessly and unintendedly. Because the medical fluid injector 10 discharges the medical fluid upon pressing of the push button, the unintended pressing of the push button 12 leads to an unnecessary injection of the medical fluid.
Since an injection needle for injecting medical fluid is inserted into one arm of the patient, the patient generally operates the medical fluid injector 10 by using the hand of the other arm. In such a case, as illustrated in FIG. 1, the patient puts the flattened housing body 11 of the medical fluid injector 10 on the palm and pushes the push button 12 with the thumb. However, it is not easy for the patient to operate the medical fluid injector 10, which includes the flattened housing body 11 and the push button 12 located on the upper surface of the housing body, with only one hand. And in the state where the patient grips the flattened housing body 11, the patient cannot easily push the push button 12 located on the upper surface of the housing body 11 with his thumb. As such, the medical fluid injector 10 of the prior art fails to provide satisfactory user convenience.